Ok, i started a game with a buddy to be a lot like minecraft, you start with nothing, not even clothing, and you need to explore and make everything yourself. These are the basic rules i came up with, and i am looking for input on how to refine things.

Iron is found from searching in bogs (marshes) before being found underground. DC 15 to find (d8*d8)
Clay is found in wet areas under the surface.

1 pound of iron is 1sp after smelting

A Basic Smithy is 500gp and comes with all the tools
ie 16667 CP + 150lbs of iron + 150lbs of wood + 250lbs of clay.
Consumes 5lbs of wood for every pound of iron used

*only after smithy is made can you craft any metal objects*

Shovel is needed for digging, (5sq ft/4hours) [5x5x5/16hours] making it with iron doubles the speed.
Base DC is 15 but 10 with iron shovel (20 with bare hands)
Roll for every 4 hours you spend working.

Success > You make progress = 4 hours of work
Failure > You make progress = 2 hours of work

For every 5 degrees of success or failure add/subtract 1 hour from progress

Digging near water will take twice as long if you want to keep the water from filling in the hole but D8+1 lbs of clay is found in each new block you dig. Digging only for clay takes half the base time.
(50% chance of DC +5 due to rocks)

Digging in forests adds 5 to the DC due to roots.

Iron Picks are needed for digging through stone (3gp and 10lbs 8lbs of iron and 2lbs of wood)

Digging through stone is 4 times as intensive work.

While digging horizontal any roll of 1 causes a cave in unless reinforced (200lbs of wood per section)